Members of the British parliament called Donald Trump everything from a buffoon to a race-baiting terrorist enabler Monday — but stopped short of endorsing a ban on allowing him to enter the United Kingdom, saying they didn’t want to turn him into a political martyr.

Though insisting they didn’t intend to insult Americans as a whole, the lawmakers had little good to say about Mr. Trump, the front-runner for Republicans’ presidential nomination, as they engaged in a three-hour debate on a petition to exclude him from the country.

The members said the decision on barring his entry actually belonged to the home secretary, not Parliament, so the debate was symbolic. But they nonetheless praised themselves for hosting the debate, saying it sent a signal that they were worried about politics across the Atlantic.

“His comments regarding Muslims are wrong, his policy to close borders if he is elected as president is bonkers, and if he met one or two of my constituents in one of the may excellent pubs in my constituency then they may well tell him he is a wazzock for dealing with this issue in this way,” said Victoria Atkins, a conservative member of Parliament.

Being called a “Wazzock” — a British insult akin to being labeled a blowhard — was one of the softer attacks on Mr. Trump, who was also dubbed “poisonous,” “homophobic,” “racist” and a “ridiculous xenophobe.” He was also accused of advocating “stupidity.”

Mr. Trump sparked international protests with his calls for a halt to Muslim visits and immigration to the U.S. after a spate of terrorist attacks late last year, perpetrated at least partly by migrants who were radicalized overseas.

The GOP presidential candidate’s accusation that Mexico sends rapists and other bad elements to the U.S., and his mocking of a disabled journalist last year also drew complaints in the committee room.

While not mentioning the British debate, Mr. Trump in a speech at Liberty University on Monday defended his demand that the U.S. halt acceptance of Syria refugees.

“We cannot take a chance,” he said.

Members of Parliament said they had to hold the debate after pressure from the public, underscored by the more than half a million people who signed an online petition backing a ban on the billionaire businessman.

Under British law, the home secretary can exclude someone from entering the country if he or she is deemed to be a danger to the public good.

Those who have been excluded in recent years include the leader of a violent gang that attacked migrants and captured the beatings on video, posting them on the Internet, and a preacher deemed to have fomenting terrorist violence.

Some members of Parliament said it was wrong to include Mr. Trump in that list, saying that while they don’t agree with his calls, he’s capturing a sentiment that’s prevalent in the immigration and security debate.

But Tulip Siddiq, a Labour Party member, said Mr. Trump’s rhetoric has spurred racist violence. She pointed to a report from Boston last year where police said two white thugs beat a homeless Hispanic man and later told investigators Mr. Trump “was right” about the need to deport “all these illegals.”

“There is a very real correlation between the words Donald Trump is using and the increase in hate crime,” said Ms. Siddiq, who is Muslim.

The closest to a defense for Mr. Trump came from lawmakers who said his candor should be refreshing, even for those who don’t agree with it.

“It takes real guts to say things unpopular and controversial,” said Philip Davies, a conservative member who said backing Mr. Trump’s right to speak was a critical defense of the right to free speech.